Low thermal conducting spacer assembly for an insulating glazing unit and method of making same

ABSTRACT

An insulating unit has a pair of glass sheets about an edge assembly to provide a compartment between the sheets. The edge assembly has a U-shaped spacer made of metal, metal coated plastic, gas and moisture impervious polymer, or gas and moisture impervious film coated polymer. The outer legs of the spacer and the glass provide a long diffusion path to limit the diffusion of argon gas out of the compartment. The edge assembly has materials selected and sized to provide edge assembly having an RES-value of at least 75. A spacer for use in insulating units includes a plastic core having a gas impervious film e.g. a metal film or a halogenated polymer film. Also taught herein are techniques for making the unit and spacer.

RELATED APPLICATION

This is a continuation-in-part application of U.S. patent applicationSer. No. 07/578,696 filed on Sep. 4, 1990, in the names of Stephen C.Misera and William R. Siskos and entitled INSULATING GLAZING UNIT HAVINGA LOW THERMAL CONDUCTING EDGE AND METHOD OF MAKING SAME.

The unit taught in this application may be fabricated using the spacerand spacer frame disclosed in U.S. patent application Ser. No.07/578,697 filed on Sep. 4, 1990, in the names of Stephen C. Misera andWilliam Siskos and entitled A SPACER AND SPACER FRAME FOR AN INSULATINGGLAZING UNIT AND METHOD OF MAKING SAME.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to an insulating glazing unit and a method ofmaking same and, in particular, to an insulating glazing unit having anedge assembly to provide the unit with a low thermal conducting edge,i.e. high resistance to heat flow at the edge of the unit.

2. Discussion of Available Insulating Units

It is well recognized that insulating glazing units reduce heat transferbetween the outside and inside of a home or other structures. A measureof insulating value generally used is the “U-value”. The U-value is themeasure of heat in British Thermal Unit (BTU) passing through the unitper hour (Hr)−square foot (Sq.Ft.)−degree Fahrenheit (° F.)$\left( \frac{BTU}{{Hr}\text{-}{{Sq}.{Ft}.{{^\circ}F}}} \right).$

As can be appreciated the lower the U-value the better the thermalinsulating value of the unit, i.e. higher resistance to heat flowresulting in less heat conducted through the unit.Another measure of insulating value is the “R-value” which is theinverse of the U-value. Still another measure is the resistance (RES) toheat flow which is stated in Hr−° F. per BTU per inch of perimeter ofthe unit $\left( \frac{{Hr} - {{^\circ}F}}{{BTU}/{in}} \right).$

In the past the insulating property, e.g. U-value given for aninsulating unit was the U-value measured at the center of the unit.Recently it has been recognized that the U-value of the edge of the unitmust be considered separately to determine the overall thermalperformance of the unit. For example, units that have a low centerU-value and high edge U-value during the winter season exhibit nomoisture condensation at the center of the unit, but may havecondensation or even a thin line of ice at the edge of the unit near theframe. The condensation or ice at the edge of the unit indicates thatthere is heat loss through the unit and/or frame i.e. the edge has ahigh U-value. As can be appreciated, when the condensate or water fromthe melting ice runs down the unit onto wooden frames, the wood, if notproperly cared for, will rot. Also, the larger temperature differencesbetween the warm center and the cold edge can cause greater edge stressand glass breakage. The U-values of framed and unframed units andmethods of determining same are discussed in more detail in the sectionentitled “Description of the Invention.”

Through the years, the design of and construction materials used tofabricate insulating glazing units, and the frames have improved toprovide framed units having low U-values. Several types of unitspresently available, and center and edge U-values of selected ones, areconsidered in the following discussion.

Insulating glass edge units which are characterized by (1) the edges ofthe glass sheets welded together, (2) a low emissivity coating on onesheet and (3) argon in the space between the sheets are taught, amongother places, in U.S. patent application Ser. No. 07/468,039 assigned toPPG Industries, Inc. filed on Jan. 22, 1990, in the names of P. J.Kovacik et al. and entitled “Method of and Apparatus for Joining Edgesof Glass Sheets, One of Which Has an Electroconductive Coating and theArticle Made Thereby.” The units taught therein have a measured centerU-value of about 0.25 and a measured edge U-value of about 0.55.Although insulating units of this type are acceptable, there arelimitations. For example, special equipment is required to heat and fusethe edges of the glass sheets together, and tempered glass is not usedin the construction of the units.

In U.S. Pat. No. 4,807,439 there is taught an insulting unit marketed byPPG Industries, Inc. under the registered trademark SUNSEAL. The unithas a pair of glass sheets spaced about 0.45 inch (1.14 centimeters)apart about an organic edge assembly and air in the compartment betweenthe sheets. A unit so constructed is expected to have a measured centerU-value of about 0.35 and an edge U-value of about 0.59. Althoughproviding insulating gas e.g. argon in the unit would lower the centerand edge U-values, the argon in time would diffuse through the organicedge assembly raising the center and edge U-values to those valuespreviously stated.

The unit of U.S. Pat. No. 4,831,799 has an organic edge assembly and agas barrier coating, sheet or film at the peripheral edge of the unit toretain argon in the unit. The thermal performance of the unit isdiscussed in column 5 of the patent. U.S. Pat. Nos. 4,431,691 and4,873,803 each teach a unit having a pair of glass sheets separated byan edge assembly having an organic bead having a thin rigid memberembedded therein. Although the units of these patents have acceptableU-values, they have drawbacks. More particularly, the units have a shortlength, high resistance diffusion path. The diffusion path is thedistance that gas, e.g. argon, air, or moisture has to travel to exit orenter the compartment between the sheets. The resistance of thediffusion path is determined by the permeability, thickness and lengthof the material. The units taught in U.S. Pat. Nos. 4,831,799; 4,431,691and 4,873,803 have a high resistance, short diffusion path between themetal strip or spacing means and the glass sheets; the remainder of theedge assembly has a low resistance, long length diffusion path.

In U.S. Pat. No. 3,919,023, there is taught an edge assembly for aninsulating unit that provides a high resistance, long length diffusionpath that may be used to minimize the loss of argon. A limitation of theedge assembly of the patent is the use of a metal strip around the outermarginal edges of the unit. This metal strip conducts heat around theedge of the unit, and the unit is expected to have a high edge U-value.

It was mentioned that the effect of the frame U-value on the window edgeU-value should be taken into account; however, a detailed discussion offrames having low U-value is omitted because the instant invention isdirected to an insulating glazing unit that has low center and edgeU-values, is easy to construct, does not have the limitations ordrawbacks of the presently available insulating glazing units, and maybe used with any frame construction.

SUMMARY OF THE INVENTION

The invention covers an insulating unit having a pair of glass sheetsseparated by an edge assembly to provide a sealed compartment betweenthe sheets having a gas therein. The edge assembly includes a spacerthat is structurally sound to maintain the glass sheets in a fixedspaced relationship and yet accommodates a certain degree of thermalexpansion and contraction which typically occurs in the severalcomponent parts of the insulating glazing unit. A diffusion path havingresistance to the gas in the compartment e.g. a long thin diffusionpath, is provided between the spacer and the glass sheets, and the edgeassembly has a high RES value at the unit edge as determined using theANSYS program.

The invention also covers a method of making an insulating unit. Themethod includes the steps of providing an edge assembly between a pairof glass sheets to provide a compartment therebetween. The edge assemblyis fabricated by providing a pair of glass sheets; selecting astructurally resilient spacer, sealant materials and moisture perviousdesiccant containing material to provide an edge assembly having a highRES as determined using the ANSYS program and a long thin diffusionpath. The glass sheets, spacer, sealant material and desiccantcontaining materials are assembled to provide an insulating unit havinga high RES at the edge as measured using the ANSYS program.

The preferred insulating unit of the invention has an environmentalcoating, e.g. a low-E coating on at least one sheet surface. Adhesivesealant on each of the outer surfaces of the spacer having a “U-shaped”cross section secures the sheets to the spacer. A strip of moisturepervious adhesive having a desiccant is provided on the inner surface ofthe spacer.

Further, the invention covers a spacer that may be used in theinsulating unit. The spacer includes a structurally resilient core e.g.a plastic core having a moisture/gas impervious film e.g. a metal filmor a halogenated polymeric film such as polyvinylidene chloride orflouride or polyvinyl chloride or polytrichlorofluoro ethylene.

Additionally, the spacer may be made entirely from a polymeric materialhaving both structural resiliency and moisture/gas imperviouscharacteristics such as a halogenated polymeric material includingpolyvinylidene chloride or flouride or polyvinyl chloride orpolytrichlorofluoro ethylene.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1 thru 4 are cross sectional views of edge assemblies of prior artinsulating units.

FIG. 5 is a plan view of an insulating unit having a generic spacerassembly.

FIG. 6 is a view taken along lines 6-6 of FIG. 5.

FIG. 7 is the left half of the view of FIG. 6 showing heat flow linesthrough the unit.

FIG. 8 is a view similar to the view of FIG. 7 having the heat flowlines removed.

FIG. 9 is a graph showing edge temperature distribution for units havingvarious type of edge assemblies.

FIG. 10 is a sectional view of an edge assembly incorporating featuresof the invention.

FIG. 11 is a cross section of another embodiment of a spacer of theinstant invention.

FIG. 12 is a view of an edge strip incorporating features of theinvention having a bead of a moisture and/or gas pervious adhesivehaving a desiccant.

FIG. 13 is a side elevated view of a roll forming station to form theedge strip of FIG. 12 into spacer stock incorporating features of theinstant invention.

FIGS. 14 thru 16 are views taken along lines 14 thru 16 respectively ofFIG. 13.

FIG. 17 is a view of a continuous corner of a spacer frame of theinstant invention made using the spacer section shown in FIG. 18.

FIG. 18 is a partial side view of a section of spacer stock notched andcreased prior to bending to form the continuous corner of the spacerframe shown in FIG. 17 in accordance to the teachings and incorporatingfeatures of the inventions.

FIG. 19 is a view similar to the view of FIG. 18 illustrating anothercontinuous corner of a spacer frame incorporating features of theinvention.

FIG. 20 is a view similar to the view of FIG. 10 showing anotherembodiment of the invention.

DESCRIPTION OF THE INVENTION

In the following discussion like numerals refer to like elements, andthe units are described having two glass sheets; however, as isappreciated by those skilled in the art, units with more than two sheetsas shown in FIG. 20 are also contemplated.

With reference to FIGS. 1-4 there are shown four general types of priorart edge assemblies used in the construction of insulated glazing units.Unit 10 of FIG. 1 includes a pair of glass sheets 12 and 14 spaced fromone another by an edge assembly 16 to provide a compartment 18 betweenthe sheets. The edge assembly 16 includes a hollow metal spacer 20having a desiccant 22 therein to absorb any moisture in the compartmentand holes 23 (only one shown in FIG. 1) providing communication betweenthe desiccant and the compartment. The edge assembly 16 further includesan adhesive type sealant 24 e.g. silicon at the lower section of thespacer 20 as viewed in FIG. 1 to secure the spacer 20 and the glasssheets together and a sealant 25 e.g. a butyl sealant at the uppersection of the spacer 20 to prevent the egress of insulating gas in thecompartment 18. The edge assembly 16 of the unit 10 is similar to thetype of units sold by Cardinal Glass and also similar to the insulatingunits taught in U.S. Pat. Nos. 2,768,475; 3,919,023; 3,974,823;4,520,611 and 4,780,164 which teachings are hereby incorporated byreference.

Unit 30 in FIG. 2 includes the glass sheets 12 and 14 having their edgeswelded together at 32 to provide the compartment 18. One of the glasssheets e.g. sheet 12 has a low emissivity coating 34. The unit 30 shownin FIG. 2 is similar to the insulating units sold by PPG Industries,Inc. under its trademark OptimEdge and is also similar to the unitstaught in U.S. Pat. Nos. 4,132,539 and 4,350,515 and in U.S. patentapplication Ser. No. 07/468,039 filed on Jan. 22, 1990, discussed above,which teachings are hereby incorporated by reference.

With reference to FIG. 3 there is shown unit 50 taught in U.S. Pat. No.4,831,799, which teachings are hereby incorporated by reference. Theunit 50 has the glass sheets 12 and 14 separated by an edge assembly 52to provide the compartment 18. The edge assembly 52 includes a moisturepervious foam material 54 having a desiccant 56 therein to absorbmoisture in the compartment 18, a moisture impervious sealant 58 toprevent moisture in the air from moving into the compartment 18 and agas barrier coating, sheet or film 60 between the foam material 54 andsealant 58 to prevent egress of the insulating gas in the compartment18. Units similar to the unit 50 are taught in U.S. Pat. No. 4,807,419which teachings are hereby incorporated by reference.

In FIG. 4 there is shown unit 70 taught in U.S. Pat. Nos. 4,431,691 and4,873,803 which teachings are hereby incorporated by reference. The unit70 has the glass sheets 12 and 14 separated by an edge assembly 72 toprovide the compartment 18. The edge assembly 72 includes a moisturepervious adhesive 74 having a desiccant 76 and a metal member 78therein.

Before teaching the construction of the insulating unit, moreparticularly the edge assembly of the instant invention, a discussion ofthe heat transfer through an insulated unit is deemed appropriate tofully appreciate the instant invention. In the following discussion theU-value will be used to compare or rate heat transfer i.e. resistance toheat flow through a glazing unit to reduce heat loss. As is appreciatedby those skilled in the art the lower the U-value the less heat transferand vice versa. The U-value for an insulating unit can be determinedfrom the following equation.Ut=(Ac/At)Uc+(Ae/At)Ue+(Af/At)Uf  (1)

where

-   -   U is the measure of heat transfer in British Thermal        Unit/hour−square foot−° F. (BTU/Hr−Sq.Ft.−° F.)    -   A is area under consideration in square feet    -   c designates the center of the unit    -   e designates the edge of the unit    -   f designates the frame    -   t is total unit value of the parameter under discussion        Shown in FIGS. 5 and 6 is a generic insulating unit 90 having        the glass sheets 12 and 14 separated by an edge assembly 92 to        provide the compartment 18. The edge assembly 92 is considered        for the purposes of this discussion a generic edge assembly and        is not limited by design. With specific reference to FIG. 5, the        unit 90 for purposes of the discussion has an edge area 94 which        is the area between the peripheral edge 95 of the unit and a        position about 3.0 inches (7.62 centimeters) in from the        peripheral edge, and a central area 96. The interface between        the edge area 94 and center area 96 of the unit 90 is shown in        FIG. 5 by dotted lines 98.

The left half of unit 90 shown in FIG. 6 is shown in FIG. 7 having thenumerals removed for purposes of clarity during the following discussionrelating to heat transfer through the unit. With reference to FIGS. 5, 6and 7 as required, during the winter season, heat from inside anenclosure e.g. a house moves through the edge area 94 and center area 96of the unit 90 to the outside. Referring now to FIG. 7, at the centerarea 96 of the unit, the heat flow pattern is generally perpendicular tothe isotherm which is the major surfaces of the glass sheets 12 and 14and is illustrated in FIG. 7 by arrowed lines 100. The direction of theheat flow pattern changes as the peripheral edge 95 of the unit isapproached as illustrated by arrowed lines 102, until at the peripheraledge 95 of the unit the heat flow pattern is again perpendicular to themajor surface of the glass sheets as illustrated by arrowed lines 104.As can be appreciated by those skilled in the art, a frame mounted aboutthe periphery of the unit has an effect on the flow patterns, inparticular, flow patterns 102 and 104. For purposes of this discussionthe effect of the frame on flow patterns 102 and 104 is omitted, and theabove discussion is considered sufficient to provide a background toappreciate the instant invention.

The heat flow through the center area 96 of the unit 90 may be modifiedby changes in the thermal properties of sheets 12 and 14, the distancebetween the sheets and gas in the compartment 18. Consider now thedistance between the sheets i.e. the compartment spacing. Compartmentshaving a spacing between about 0.250-0.500 inch (0.63-1.27 centimeters)are considered acceptable to provide an insulating gas layer with thepreferred spacing depending on the insulating gases used. Krypton gas ispreferred at the low range, air and argon are preferred at the upperrange. In general, below 0.250 inch (0.63 centimeter) the spacing is notwide enough e.g. for air or argon gas to provide a significantinsulating gas layer and above 0.500 inch (1.27 centimeters), gascurrents e.g. using krypton gas in the compartment have sufficientmobility to allow convection thereby moving heat between the glasssurfaces, e.g. between the glass surface facing the house interior tothe glass surface facing the house exterior.

As previously mentioned, heat flow through the unit may also be modifiedby the type of gas used in the compartment. For example, using a gasthat has a high thermal insulating value increases the performance ofthe unit, in other words it decreases the U-value at the center and edgeareas of the unit. By way of example, but not limiting to the invention,argon has a higher thermal insulating value than air. Everything elserelating to the construction of the unit being equal, using argon wouldlower the U-value of the unit.

Another technique to modify the thermal insulating value of the centerarea is to use sheets having high thermal insulating values and/orsheets having low emissivity coatings. Types of low emissivity coatingsthat may be used in the practice of the invention are taught in U.S.Pat. Nos. 4,610,771; 4,806,220; and 4,853,256 which teachings are herebyincorporated by reference. Also increasing the number of glass sheetsincreases the number of compartments thereby increasing the insulatingeffect at the center and edge areas of the unit.

The discussion will now be directed to the thermal loss at the edge areaof the unit. With reference to FIG. 8 there is shown an edge portion ofthe unit 90 shown in FIGS. 5 and 6. The letters A and E are the pointswhere heat flow is generally perpendicular to the glass surfaces. As theedge of the unit is approached the glass begins to act as an extendedsurface relative to the edge and causes the heat flow paths 100 to curveor bend at the edge of the unit as illustrated in FIG. 7 by numerals102. This curvature occurs in the edge area 94 shown in FIGS. 6 and 7.Between the letters B and D the flow of heat is primarily resisted bythe edge assembly 92 rather than the glass at the unit edge. Withreference to FIG. 9 curves 120, 130 and 140 show the edge heat loss fordifferent types of edge assemblies. FIG. 9 should not be interpreted asan absolute relationship but as a general guide to better understand theheat flow through the edge assembly. Curve 120 illustrates the heat losspattern for an edge assembly that is highly heat conductive e.g. analuminum spacer generally used in the construction of edge assemblies ofthe types shown in FIG. 1. Curve 130 illustrates the heat loss patternfor an edge assembly that is less heat conductive than an edge assemblyhaving an aluminum spacer e.g. an edge assembly having a plastic spacersimilar to the construction of the edge assembly shown in FIG. 3. Line140 illustrates the edge heat loss pattern for a glass edge unit of thetype shown in FIG. 2. Although not limiting to the invention, the edgeassembly incorporating features of the invention is expected to providea heat loss pattern similar to curve 140 and heat loss patterns withinthe shaded areas between curves 130 and 140.

As can be seen in FIG. 9, the profile for an aluminum spacer representedby the curve 120 shows that the aluminum spacer at the edge of the unit(between points A and C) offers little resistance to heat flow thusallowing a cooler edge at the surface of the unit inside the house. Theprofile for an organic e.g. polymeric spacer represented by the curve130 shows the organic spacer to have a high resistance to heat flowallowing for a warmer glass surface inside the house resulting inreduced heat loss at the edge of the unit. This is particularlyillustrated by the curve 130 between points A and C. Edges of weldedglass sheets e.g. as shown in FIG. 2 offer more resistance than themetal type spacer assembly but less than the plastic type edge assembly.The temperature distribution of edge welded units between points A and Cis represented by the line 140 which is between lines 120 and 130between points A and C on the graph of FIG. 9.

The heat loss for an edge assembly using a metal spacer, in particularan aluminum spacer is greater than for glass because the aluminum spacerhas a higher thermal conductivity (aluminum is a better conductor ofheat than glass or organic materials). The effect of the higher thermalconductivity of the aluminum spacer is also evident at point D whichshows the curve 120 for the aluminum spacer to have a higher temperaturethan the curve 140 or the curve 130 at the outside surface of the unit.The heat to maintain the higher temperature at D for the aluminum spaceris conducted from inside the house thereby resulting in a heat loss atthe edge of the unit greater than the edge heat loss for units havingglass or organic spacers, and greater than the edge assembly of theinvention as will be discussed in detail below.

The heat loss for an edge assembly having an organic spacer is less thanthe heat loss for edge assemblies having metal spacers or welded glassbecause the organic spacer has a lower thermal conductivity. The effectof the lower thermal conductivity of the organic spacer is shown by line130 at point D which has a lower temperature than the glass and metalspacers illustrating that conductive heat loss through the organicspacer is less than for glass and metal spacers.

A phenomenon of units having high edge heat loss is that on very colddays, a thin layer of condensation or ice forms at the inside of theunit at the frame. This ice or condensate may be present even though thecenter of the unit is free of moisture.

As was discussed, units that have argon in the compartment and polymericedge assemblies may have an initial low U-value, but as time passes, theU-value increases because polymeric spacers as a general rule do notretain argon. To retain argon an additional film such as that taught inU.S. Pat. No. 4,831,799 is required. The drawback of the unit of thisU.S. Pat. No. 4,831,799 is that the film has a short diffusion path aswas discussed supra. As can be appreciated argon retention can beimproved by selection of materials e.g. hot melt adhesive sealants suchas HB Fuller 1191, HB Fuller 1081A and PPG Industries, Inc. 4442 butylsealant retain argon better than most polyurethane adhesives.

With reference to FIG. 10 there is shown insulating unit 150 having edgeassembly 152 incorporating features of the invention to space the glasssheets 12 and 14 to provide the compartment 18. The edge assembly 152includes a moisture and/or gas impervious adhesive type sealant layer154 to adhere the glass sheets 12 and 14 to legs 156 of metal spacer158. The sealant layers 154 act as a barrier to moisture entering theunit and/or a barrier to gas e.g. insulating gas such as argon fromexiting the compartment 22. With respect to the loss of the fill gasfrom the unit, in practice the length of the diffusion path andthickness of the sealant bead are chosen in combination with the gaspermeability of sealant material so that the rate of loss of the fillgas matches the desired unit performance lifetime. The ability of theunit to contain the fill gas is measured using a European procedureidentified as DIN 52293. Preferably, the rate of loss of the fill gasshould be less than 5% per year and more preferably it should be lessthan 1% per year.

With respect to the ingress of moisture into the unit, the geometry ofthe sealant bead is chosen so that the amount of moisture permeatingthrough the perimeter parts (i.e. sealant bead and spacer) is a quantityable to be absorbed into the quantity of desiccant within the unit overthe desired unit lifetime. The preferred adhesive sealant to be usedwith the spacer of FIGS. 10 and 11 should have a moisture permeabilityof less than 20 gm mm/M² day using ASTM F 372-73. More preferably, thepermeability should be less than 5 gm mm/M² day.

The relationship between the amount of desiccant in the unit and thepermeability of the sealant (and its geometry) may be varied dependingon the overall desired unit lifetime.

An additional adhesive sealant type layer or structural adhesive layer155 e.g. but not limited to silicone adhesive and/or hot melts may beprovided in the perimeter groove of the unit formed by middle leg 157 ofthe spacer and marginal edges of the glass sheets. As can now beappreciated the sealant is not limiting to the invention and may be anyof the types known in the art e.g. the type taught in U.S. Pat. No.4,109,431 which teachings are hereby incorporated by reference. A thinlayer 160 of a moisture pervious adhesive having a desiccant 162 thereinto absorb moisture in the compartment 18 is provided on the innersurface of the middle leg 157 of the spacer 158 as viewed in FIG. 10.The desiccant may also be placed along the inner surface of the legs 156as well as the middle leg 157. The permeability of the adhesive layer160 is not limiting to the invention but should be sufficientlypermeable to moisture within compartment 18 so that the desiccanttherein can absorb moisture within the compartment. Adhesive materialshaving a permeability of greater than 2 gm mm/M² day as determined bythe above referred to ASTM F 372-73 may be used in the practice of theinvention. The edge assembly 152 provides the unit 150 with a lowthermal conductive path through the edge i.e. a high resistance to heatloss, a long diffusion path and structural integrity with sufficientstructural resilience to accommodate a certain degree of thermalexpansion and contraction which typically occurs in the severalcomponent parts of the insulating glazing unit.

To fully appreciate the high resistance to heat loss of the edgeassembly of the instant invention, the following discussion of themechanism of thermal conductivity through the edge of an insulated unitis presented.

The heat loss through an edge of a unit is a function of the thermalconductivity of the materials used, their physical arrangement, thethermal conductivity of the frame and surface film coefficient. Surfacefilm coefficient is transfer of heat from air to glass at the warm sideof the unit and heat transfer from glass to air on the cold side of theunit. The surface film coefficient depends on the weather and theenvironment. Since the weather and environment are controlled by natureand not by unit design, no further discussion is deemed necessary. Theframe effect will be discussed later leaving the present discussion tothe thermal conductivity of the materials at the unit edge and theirphysical arrangement.

The resistance of the edge of the unit to heat loss for an insulatingunit having sheet material separated by an edge assembly is given byequation (2).RHL=G ₁ +G ₂ + . . . +G _(n) +S ₁ +S ₂ + . . . +S _(n)  (2)

where

-   -   RHL is the resistance to edge heat loss at the edge of the unit        in hour−° F./BTU/inch of unit perimeter (Hr−° F./BTU/in.)    -   G is the resistance to heat loss of a sheet in Hr−° F./BTU/in.    -   S is the resistance to heat loss of the edge assembly in Hr−°        F./BTU/in.        For an insulating unit having two sheets separated by a single        edge assembly equation (2) may be rewritten as equation (3).        RHL=G ₁ +G ₂ +S ₁  (3)

The thermal resistance of a material is given by equation (4).R=L/KA  (4)

where

-   -   R is the thermal resistance in Hr−° F./BTU/in.    -   K is thermal conductivity of the material in BTU/hour−inch−° F.    -   L is the thickness of the material as measured in inches along        an axis parallel to the heat flow.    -   A is the area of the material as measured in square inches along        an axis transverse to the heat flow/in. of perimeter.

The thermal resistance for components of an edge assembly that lie in aline substantially perpendicular or normal to the major surface of theunit is determined by equation (5).S=R ₁ +R ₂ + . . . +R _(n)  (5)

where S and R are as previously defined.

In those instances where the components of an edge assembly lie along anaxis parallel to the major surface of the unit, the thermal resistance(S) is defined by the following equation (6). $\begin{matrix}{S = \frac{1}{\frac{1}{R_{1}} + \frac{1}{R_{2}} + \ldots + \frac{1}{R_{n}}}} & (6)\end{matrix}$

where R is as previously defined.

Combining equations (3), (5) and (6) the resistance of the edge of theunit 150 shown in FIG. 10 to heat flow may be determined by followingequation (7). $\begin{matrix}{{RHL} = {R_{12} + R_{14} + {2R_{154}} + {2R_{156}} + \frac{1}{\frac{1}{R_{157}} + \frac{1}{R_{160}} + \frac{1}{R_{155}}}}} & (7)\end{matrix}$

where

-   -   RHL is as previously defined,    -   R₁₂ and R₁₄ are the thermal resistance of the glass sheets,    -   R₁₅₄ is the thermal resistance of the adhesive layer 154,    -   R₁₅₅ is the thermal resistance of the adhesive layer 155,    -   R₁₅₆ is the thermal resistance of the outer legs 156 of the        spacer 158,    -   R₁₅₇ is the thermal resistance of the middle leg 157 of the        spacer 158, and    -   R₁₆₀ is the thermal resistance of the adhesive layer 160.

Although equation (7) shows the relation of the components to determineedge resistance to heat loss, Equation 7 is an approximate method usedin standard engineering calculations. Computer programs are availablewhich solve the exact relations governing heat flow or resistance toheat flow through the edge of the unit.

One computer program that is available is the thermal analysis packageof the ANSYS program available from Swanson Analysis Systems Inc. ofHouston, Pa. The ANSYS program was used to determine the resistance toedge heat loss or U-value for units similar to those shown in FIGS. 1-4.

The edge U-value, defined previously, while being a measure of theoverall effect demonstrating the utility of the invention is highlydependent on certain phenomena that are not limiting to the inventionsuch as film coefficients, glass thickness and frame construction. Thediscussion of the edge resistance of the edge assembly (excluding theglass sheets) will now be considered. The edge resistance of the edgeassembly is defined by the inverse of the flow of heat that occurs fromthe interface of the glass and sealant layer 154 at the inside side ofthe unit to the interface of glass and sealant layer 154 at the outsideside of the unit per unit increment of temperature, per unit length ofedge assembly perimeter. The glass sealant interfaces are assumed to beisothermal to simplify the discussion. Support for the above positionmay be found, among other places, in the paper entitled ThermalResistance Measurements of Glazing System Edge-Seals and Seal MaterialsUsing a Guarded Heater Plate Apparatus written by J. L. Wright and H. F.Sullivan ASHRAE TRANSACTIONS 1989, V.95, Pt. 2.

In the following discussion and in the claims, a parameter of interestis the resistance to heat flow of the edge assembly per unit length ofperimeter (“RES”).

As mentioned above, the ANSYS finite element code was used to determinethe RES. The result of the ANSYS calculation is dependent on the assumedgeometry of the cross section of the edge assembly and the assumedthermal conductivity of the constituents thereof. The geometry of anysuch cross section can easily be measured by studying the unit edgeassembly. The thermal conductivity of the constituents or the edgeassembly RES value can be measured as shown in ASHRAE TRANSACTIONSidentified above. The following thermal conductivity values for edgeassembly materials are given in the article. Additional values may befound in Principles of Heat Transfer 3rd ed. by Frank Kreith. MaterialThermal Conductivity Butyl .24 W/mC (.011 BTU/hr-in-° F.) Silicone .36W/mC (.017 BTU/hr-in-° F.) Polyurethene .31 W/mC (.014 BTU/hr-in-° F.)304 stainless steel 13.8 W/mC (.667 BTU/hr-in-° F.)  Aluminum 202. W/mC(9.75 BTU/hr-in-° F.) 

Let us now consider the RES calculated for edge assemblies of the unitsof FIGS. 1-4. The construction of the edge assembly 16 of the unit 10 ofFIG. 1 included a hollow aluminum spacer 20 between the glass sheets;the spacer had a wall thickness of about 0.025 inch (0.06 centimeter), aside length perpendicular to the major surface of the glass sheets 12and 14 of about 0.415 inch (1.05 centimeters), and a side lengthgenerally parallel to the major surface of the glass sheets 12 and 14 ofabout 0.3 inch (0.76 centimeter); adhesive layers 24 of butyl having athickness of about 0.003 inch (0.008 centimeter); and a siliconestructural seal 16 filling the cavity formed by the spacer 20 and glasssheets 12 and 14. The edge assembly RES-value of the unit (10)constructed as above discussed using the ANSYS program was calculated tobe 4.65 hr−° F./BTU per inch of perimeter.

The construction of the edge assembly 32 of the unit 30 of FIG. 2included a pair of glass sheets spaced about 0.423 inch (1.07centimeters) apart; an edge wall designated by number 32 having athickness of about 0.090 inch (0.229 centimeter). The edge assemblyRES-value of the unit 30 constructed as described above using the ANSYSprogram was calculated to be 104 hr−° F./BTU per inch of perimeter.

The construction of the edge assembly 52 of the unit 50 of FIG. 3included a pair of glass sheets 12 and 14 spaced about 0.50 inch (1.27centimeters) apart; a desiccant filled foam structural member about 0.25inch (0.64 centimeter) thick adhered to the glass surfaces; an aluminumcoated plastic diffusion barrier and a butyl edge seal about 0.25 inch(0.64 centimeter) thick. The aluminum coating between the foam memberand seal was too thin for accurate measurement. The edge assemblyRES-value of the unit 50 constructed as above described using the ANSYSprogram was calculated to be 104.0 hr−° F./BTU per inch of perimeter.

A unit similar to the unit 50 of FIG. 3 having a pair of glass sheets 12and 14 spaced 0.45 inch (1.143 centimeters) apart; an adhesive layer 54of silicone having a thickness of about 0.187 inch (0.475 centimeter)with desiccant therein; a moisture impervious sealant 58 of butyl havinga thickness of about 0.187 inch (0.475 centimeter) is expected using theANSYS program to have an edge assembly RES-value using the ANSYS programof about 84.7 hr−° F./BTU per inch of perimeter. A comparison of theedge assembly RES-value for the different constructions of units of thetype shown in FIG. 3 are given to show the effect material changes anddimensions have on the edge assembly RES-value.

The construction of the edge assembly of the unit 70 of FIG. 4 includeda pair of glass sheets spaced about 0.45 inch (1.143 centimeters) apart;an adhesive butyl edge seal about 0.312 inch (0.767 centimeter) widewith a desiccant and an aluminum spacer about 0.010 inch (0.025centimeter) thick imbedded therein. The edge assembly RES-value of theunit 70 constructed as above described using the ANSYS program wascalculated to be 4.50 hr−° F./BTU per inch of perimeter.

The construction of the edge assembly 150 of the instant invention shownin FIG. 10 included a pair of glass sheets spaced about 0.47 inch (1.20centimeters) apart; a polyisobutylene layer 154 which is moisture andargon impervious had a thickness of about 0.010 inch (0.254 centimeter)and a height as viewed in FIG. 10 of about 0.250 inch (0.64 centimeter);a 304 stainless steel U-shaped channel 156 had a thickness of about0.007 inch (0.018 centimeter), the middle or center leg had a width asviewed in FIG. 10 of about 0.430 inch (1.09 centimeters) and outer legseach had a height as viewed in FIG. 10 of about 0.250 inch (0.64centimeter); a desiccant impregnated polyurethane layer 160 had a heightof about 0.125 inch (0.32 centimeter) and a width as viewed in FIG. 10of about 0.416 inch (1.05 centimeters); a polyurethane secondary seal155 had a width of about 0.450 inch (1.143 centimeters) and a height ofabout 0.125 inch (0.32 centimeter) as viewed in FIG. 10. The edgeassembly RES-value of the unit 150 constructed as above described usingthe ANSYS program was calculated to be 79.1 hr−° F./BTU per inch ofperimeter.

Shown in FIG. 11 is the cross sectional view of another embodiment of aspacer of the instant invention. Spacer 163 has a structurally resilientcore 164. The core in the practice of the invention may be non-metal andis preferably a polymeric core e.g. fiberglass reinforced plasticU-shaped member 164 having a thin film 165 of insulating gas imperviousmaterial. For example when air, argon or krypton is used in thecompartment, the thin film 165 may be metal. The structure of the spaceras well as the gas barrier film are chosen so that the unit will containthe fill gas for the desired unit lifetime. A spacer according to FIG.11 using argon as a fill gas and employing polyvinylidene chloride asthe barrier film, the preferred thickness of the polyvinylidene chloridewill be at least 5 mils and more preferably it will be greater than 10mils.

If a material other than polyvinylidene chloride is used as the barrierfilm, the proper thickness to retain the fill gas for the desired unitlifetime may be adjusted depending on the material's gas containmentcharacteristics.

The fill gas retention characteristics of the unit according to theinstant invention is measured by the above referred DIN 52293.

For argon, the film 165 may be a 0.0001 inch (0.000254 centimeter) thickaluminum film or a 0.005 inch thick film of polyvinylidene chloride. Asused herein the argon impervious material has a permeability to argon ofless than 5%/yr. The invention contemplates having a core 164 and a thinlayer of film 165 or several layers 164 and 165 to build up a laminatedstructure. Using the spacer 163 having the aluminum film in place of thespacer 155 of the unit 150 in FIG. 10 the edge assembly RES-value forthe unit 150 of FIG. 10 is expected to be about 120. This is about a 50%increase in the RES-value by changing the spacer to a thinly metalcladded plastic spacer. Using the spacer 163 having a polyvinylidenechloride film of a thickness of 0.005 inch, the edge assembly RES-valueof the unit 150 of FIG. 10 is also expected to be about 120.

The instant invention also contemplates having a spacer 163 of FIG. 11whose body is made entirely from a polymeric material havingmoisture/gas impervious characteristics. Such a spacer body may bereinforced (e.g. fiberglass reinforced) but would not include any filmbarrier (i.e. the spacer 163 would not include a thin film 165). Such apolymeric material would preferably be a halogenated polymeric materialincluding polyvinylidene chloride, polyvinylidene flouride, polyvinylchloride or polytrichlorofluoro ethylene. The edge assembly of such aspacer 163 made entirely of a polymeric material would have a high edgeassembly RES-value expected to be comparable to the spacer of FIG. 11.

The spacer of the instant invention, in addition to acting as a barrierto the insulating gas in the compartment 18, is structurally sound. Asused herein and in the claims “structurally sound” means the spacermaintains the glass sheets in a spaced relationship while permittinglocal flexure of the glass due to changes in barometric pressure,temperature and wind load. The feature of maintaining the glass sheetsin a fixed spacer relationship means that the spacer prevents the glasssheets from significantly moving toward one another when the edges ofthe unit are secured in the glazing frame. As can be appreciated lessforce is applied to the edges of residential units mounted in a woodenframe than to edges of commercial units mounted by pressure glazing inmetal curtainwall systems. Permitting local flexure means the spacerallows rotation of the marginal edge portions of the glass about itsedge during loading of the types described while restricting movementother than rotation i.e. translation. The degree of structural soundnessis related to type of material and thickness. For example metal may bethin where plastic to have the same structural soundness must be thickeror reinforced e.g. by fiber glass.

Embodiments of the instant invention may be used to improve theperformance of the prior art units. For example replacing the spacer ofthe unit 10 of FIG. 1 with a stainless steel spacer is expected toincrease the edge assembly RES-value from 4.65 to 18.2 hr−° F./BTU perunit of perimeter. If the metal thickness is changed from 0.025 inch(0.06 centimeter) to 0.005 inch (0.0127 centimeter) the edge assemblyR-value of the unit 10 of FIG. 1 using the ANSYS program goes from 4.65to 96.1 hr−° F./BTU per inch of perimeter. Replacing the aluminum stripof the unit in FIG. 4 with a stainless steel strip increases the edgeassembly RES from 4.5 to 44.4 hr−° F./BTU per unit of perimeter.

The unit 150 of the instant invention having the spacer assembly 152shown in FIG. 10 is expected to have an edge heat loss similar to thatof line 140. The unit 150 of the instant invention having the spacerassembly 163 shown in FIG. 11 is expected to have an edge heat lossbetween line 130 and 140 but close to line 130. Although the edgeassembly of the instant invention has an edge assembly RES-value lessthan the RES-value for edge assemblies having organic spacers of thetype shown in FIG. 3, the edge assembly of the instant invention hasdistinct advantages. More particularly, the spacer is metal, gas andmoisture impervious plastic, metal cladded plastic core, metal claddedreinforced plastic core, gas moisture impervious film cladded plasticcore, gas moisture film cladded reinforced plastic core and is thereforemore structurally sound. The diffusion path i.e. the length andthickness of the gas and moisture impervious adhesive sealant materialis longer in the unit of the instant invention and therefore for thesame type of material filling the diffusion path, the longer, thinnerdiffusion path of the instant invention reduces the rate of fill gasloss. The argon gas path is longer because it is limited to the adhesivelayers 154 (see FIG. 10) whereas in organic spacers the diffusion pathis through the entire width of the spacer surface. In the unit of FIG. 3a metal barrier is provided to reduce argon loss. The metal film coatedon the plastic or PVDC coated plastic has a thickness in the range ofabout 0.001-0.003 inch (0.00254-0.00762 centimeter) which is a shortdiffusion path. The instant invention has a long diffusion path e.g.greater than about 0.003 inch (0.00762 centimeter) and a thin diffusionpath e.g. less than about 0.0125 inch (0.32 centimeter). The unit shownin FIG. 10 has a diffusion path length of about 0.250 inch (0.64centimeter) and a diffusion path thickness of about 0.010 inch (0.254centimeter). The path length can be increased by increasing the heightof the legs of the spacer and the path thickness decreased by decreasingthe spacing between the legs of the spacer and adjacent glass sheet.

In actual tests a unit having an edge assembly of the instant inventionand a unit having the edge assembly shown in FIG. 3 had essentiallyidentical RES values. It is believed that the bead on the interior ofthe spacer may have insulated the spacer from convection cooling by thegases in the compartment.

As was discussed the teachings of the invention may be used to increaseedge assembly RES-value of a unit by using the spacer shown in FIG. 11.Shaping a fiberglass reinforced plastic core 164 and then sputtering athin film 165 of aluminum or adhering in any convenient manner agas/moisture impervious film such as a PVDC film prevents the egress ofargon limiting the path essentially to the sealant or adhesive betweenthe spacer and glass as was discussed for the unit 150 of FIG. 10.

As can now be appreciated the unit of the instant invention provides anedge assembly having a metal spacer, a metal coated plastic spacer or aplastic spacer or a multi-layered plastic spacer that retain insulatinggas other than air, e.g. argon, has a relatively high edge assemblyRES-value or low U-value and has structural soundness.

The discussion will now be directed to the U-value of the frame of theunit. The frame also conducts heat and in certain instances e.g. metalframes conduct sufficiently more heat than the edge assembly of the unitsuch that the edge heat loss through the frame overshadows any increasein thermal resistance to heat loss provided at the edge of the unit.Wooden frames, metal frames with thermal breaks or plastic frames havehigh resistance to heat loss and the performance of the edge heat lossof the unit would be more dominant.

The invention is not limited to units having two sheets but may bepracticed to make units having two or more sheets e.g. unit 250 shown inFIG. 20.

The discussion will now be directed to a method of fabricating theglazing unit of the instant invention. As will be appreciated the unitof the instant invention may be fabricated in any manner; however, theconstruction of the unit is discussed using selected ones of the edgeassembly components taught in U.S. patent application Ser. No.07/578,697 filed Sep. 4, 1990, in the names of Stephen C. Misera andWilliam R. Siskos and entitled A SPACER AND SPACER FRAME FOR ANINSULATING GLAZING UNIT AND METHOD OF MAKING SAME which teachings arehereby incorporated by reference.

With reference to FIG. 12, there is shown an edge strip 169 having asubstrate 170 having the bead 160 of moisture pervious adhesive havingthe desiccant 162 mixed therein. In the preferred practice of theinvention the substrate is made of a material, e.g. metal or compositeof plastic as previously described, that is moisture and gas imperviousto maintain the insulating gas in the compartment and prevent theingress of moisture into the compartment, and has structural integrityand resiliency to maintain the glass sheets in spaced relation to oneanother and yet accommodates a certain degree of thermal expansion andcontraction which typically occurs in the several component parts of theinsulating glazing unit. In the practice of the invention, the substratewas made of 304 stainless steel having a thickness of about 0.007 inch(0.0178 centimeter) thick, a width of about 0.625 inch (1.588centimeters) and a length sufficient to make spacer frame to bepositioned between glass sheets e.g. a 24-inch (0.6 meter) square shapedunit. The bead 160 is a polyurethane having a desiccant mixed therein. Abead about ⅛ inch (0.32 centimeter) high and about ⅜ inch (0.96centimeter) wide is applied to the center of the substrate 170 in anyconvenient manner.

As can be appreciated the desiccant bead may be any type of adhesive orpolymeric material that is moisture pervious and can be mixed with adesiccant. In this manner the desiccant can be contained in the adhesiveor polymer material and secured to the substrate while havingcommunication to the compartment. Types of materials that arerecommended, but the invention is not limited thereto, are polyurethanesand silicones. Further the bead may be the spacer dehydrator elementtaught in U.S. Pat. No. 3,919,023 which teachings are herebyincorporated by reference.

Further, as can now be appreciated one or both sides of one or moresheets may have an environmental coating such as the one taught in U.S.Pat. Nos. 4,610,771; 4,806,220; 4,853,256; 4,170,460; 4,239,816 and4,719,127 which patents are hereby incorporated by reference.

In the practice of the invention the metal substrate after forming intospacer stock and the bead has sufficient structural strength andresiliency to keep the sheets spaced apart and yet accommodates acertain degree of thermal expansion and contraction which typicallyoccurs in the several component parts of the insulating glazing unit. Inone embodiment of the invention the spacer is more structurally stablethan the bead i.e. the spacer is sufficiently structurally stable ordimensionally stable to maintain the sheets spaced from one anotherwhereas the bead cannot. In another embodiment of the invention both thespacer and the bead can. For example, the bead may be a desiccant in apreferred spacer taught in U.S. Pat. No. 3,919,023 to Bowser. As can beappreciated by those skilled in the art, a metal spacer can befabricated through a series of bends and shaped to withstand variouscompressive forces. The invention relating to the bead 160 carried onthe substrate 170 is defined by shaping the substrate 170 into a singlewalled U-shaped spacer stock with the resultant U-shaped spacer stockbeing capable of withstanding values of compressive force to maintainthe sheets apart regardless of the structural stability of the bead. Ascan be appreciated by those skilled in the art the measure and value ofcompressive forces and structural stability varies depending on the useof the unit. For example if the unit is secured in position by clampingthe edges of the unit such as in curtainwall systems, the spacer has tohave sufficient strength to maintain the glass sheet apart while undercompressive forces of the clamping action. When the use is mounted in arabbit of a wooden frame and caulking applied to seal the unit in place,the spacer does need as much structural stability to maintain the glasssheets apart as does a spacer of a unit that is clamped in position.

The edges of the strip 150 are bent in any convenient manner to formouter legs 156 of a spacer 158 shown in FIG. 10. For example the strip170 may be pressed between bottom and top rollers as illustrated inFIGS. 13-16.

With reference to FIG. 13 the strip is advanced from left to rightbetween roll forming stations 180 thru 185. As will be appreciated bythose skilled in the art, the invention is not limited to the number ofroll forming stations or the number of roll forming wheels at thestations. In FIG. 14 the roll forming station 180 includes a bottomwheel 190 having a peripheral groove 192 and an upper wheel 194 having aperipheral groove 196 sufficient to accommodate the layer 160. Thegroove 192 is sized to start the bending of the strip 170 to a U-shapedspacer and is less pronounced than groove 198 of the bottom wheel 200 ofthe pressing station 181 shown in FIG. 15 and the remaining bottomwheels of the downstream pressing station 182 thru 185.

With reference to FIG. 16, the lower wheel 202 of the roll formingstation 185 has a peripheral groove 202 that is substantially U-shaped.The spacer stock exiting the roll forming station 185 is the U-shapedspacer 158 shown in FIG. 10.

As can now be appreciated the grooves of the upper roll forming wheelsmay be shaped to shape the bead of material on the substrate.

In the practice of the invention the bead 160 was applied after thespacer stock was formed e.g. the substrate formed into a U-shaped spacerstock. This was accomplished by pulling the substrate through a die ofthe type known in the art to form a flat strip into a U-shaped strip.

As can be appreciated, everything else being equal, loose desiccant is abetter thermal insulation than desiccant in a moisture perviousmaterial. However, handling and containing loose desiccant in a spacerin certain instances is more of a limitation than handling desiccant ina moisture pervious matrix. Further having the desiccant in a moisturepervious matrix increases the shelf life because the desiccant takes alonger period of time to become saturated when in a moisture and/or gaspervious material as compared to being directly exposed to moisture. Thelength of time depends on the porosity of the material. However, theinvention contemplates both the use of loose desiccant and desiccant ina moisture pervious matrix.

The spacer stock 158 may be formed into a spacer frame for positioningbetween the sheets. As can be appreciated, the layers 154 and 155, shownin FIG. 10 may be applied to the spacer stock or the spacer frame. Theinvention is not limited to the materials used for the layers 154 and155; however, it is recommended that the layers 154 provide highresistance to the flow of insulating gas in the compartment 18 betweenthe spacer 152 and the sheets 12 and 14. The layer 155 may be of thesame material as layers 154 or a structural type adhesive e.g. silicone.Before or after the layers 154 and/or 155 are applied to the spacerstock, a piece of the spacer stock is cut and bent to form the spacerframe. Three corners may be formed i.e. continuous corners and thefourth corner welded or sealed using a moisture and/or gas impervioussealant. Continuous corners of spacer frame incorporating features ofthe invention are shown in FIGS. 17 and 19. However, as can beappreciated, spacer frames may be formed by joining sections of thespacer stock and sealing the edges with a moisture and/or gas impervioussealant or welding the corners together.

With reference to FIG. 18 a length of the spacer stock having the beadis cut and a notch 207 and creases 208 are provided in the spacer stockin any convenient manner at the expected bend lines. The area betweenthe creases is depressed e.g. portion 212 of the outer legs 156 at thenotch are bent inwardly while the portions on each side of the creaseare biased toward each other to provide a continuous overlying corner224 as shown in FIG. 17. The non-continuous corner e.g. the fourthcorner of a rectangular frame may be sealed with a moisture and/or gasimpervious material or welded. As can be appreciated the bead at thecorner may be removed before forming the continuous corners.

With reference to FIG. 19, in the practice of the invention spacer frame240 was formed from a U-shaped spacer stock. A continuous corner 242 wasformed by depressing the outer legs of the spacer stock toward oneanother while bending portions of the spacer stock about the depressionto form a corner e.g. 90° angle. As the portions of the spacer stock arebent the depressed portions 244 of the outer legs move inwardly towardone another. After spacer frame was formed, layers of the sealant wereprovided on the outer surface of the legs 18 of the spacer frame and thebead 26 on the inner surface of the middle leg of the spacer frame. Theunit 10 was assembled by positioning and adhering the glass sheets tothe spacer frame by the sealant layers 154 in any convenient manner.

A layer 155 of an adhesive if not previously provided on the frame isprovided in the peripheral channel of the unit (see FIG. 10) or on theperiphery of the unit. Argon gas is moved into the compartment 18 in anyconvenient manner to provide an insulating unit having a low thermalconducting edge.

As can be appreciated by those skilled in the art, the invention is notlimited by the above discussion which was presented for illustrativepurposes only.

1-32. (canceled)
 33. A method of fabricating a spacer frame formaintaining two sheets in spaced relation comprising the steps of:providing a piece of spacer stock of sufficient length to provide thespacer frame, the spacer stock having at least a pair of sidewallsjoined by a base, wherein the base and at least portions of thesidewalls form a U-shape, and further wherein at least one bead of amoisture pervious material having a desiccant therein is in contact withat least a portion of an inner surface of the spacer stock; bending thepiece of spacer stock to form the spacer frame; and maintaining at leastone bead on at least a portion of an inner surface of the spacer stockduring the practice of the bending step.
 34. The method of claim 33wherein the at least one bead of a moisture pervious material is atleast one bead of moisture pervious adhesive material.
 35. The method ofclaim 33 wherein the spacer stock is a metal spacer stock.
 36. Themethod of claim 33 wherein the spacer stock is a plastic spacer stock.37. The method of claim 33 further comprising the step of bending asubstrate to form the spacer stock having at least a pair of sidewallsjoined by a base, wherein the base and at least portions of thesidewalls provide the spacer stock with a U-shape.
 38. The method ofclaim 37 wherein the bending step is performed by roll forming thesubstrate.
 39. The method of claim 37 wherein the substrate comprises atleast one crease.
 40. The method of claim 37 wherein the at least onebead of a moisture pervious material having a desiccant therein isapplied to the substrate before the bending of the substrate.
 41. Themethod of claim 37 wherein the at least one bead of a moisture perviousmaterial having a desiccant therein is applied to the substrate afterthe bending of the substrate.
 42. The method of claim 33 wherein thebase, the at least one bead, and the at least portions of the sidewallsform a U-shape.